The present invention relates generally to orthopedic devices and, more particularly, to an orthopedic device having at least one gel pad including at least one phase change material.
In the past, a variety of different orthopedic devices have been used to treat injured ankles, legs, knees, forearms, elbows, and other body limbs and parts by immobilizing or restricting the movement of the injured joint, limb or body part. For example, my co-pending U.S. patent application, Ser. No. 07/055,711, filed May 29, 1987, describes an orthopedic ankle brace using splint members and inner liners including gel pads for engaging and supporting an injured joint or limb. Another ankle brace using an air-inflatable liner is disclosed in U.S. Pat. No. 4,280,489, issued to Johnson, Jr. on Jul. 28, 1981. Still another inflatable ankle brace using air-inflatable liners or air bags is described in U.S. Pat. No. 4,628,945, issued to Johnson, Jr. on Dec. 16, 1986. The use of foam rubber pads or liners in a lower leg brace is disclosed in U.S. Pat. No. 4,572,169, issued to Mauldin, et al. on Feb. 25, 1986.
The gel pads used in my orthopedic ankle brace referred to above provide important advantages over the above-described braces using air-inflatable liners or foam rubber pads because, in addition to other important advantages, the gel pads may be used for hot and cold temperature therapy. Increased therapeutic effect can be achieved by selectively heating or cooling the gel pads before placing the pads in my orthopedic ankle brace. My co-pending U.S. patent application, Ser. No. 07/168,681, filed Mar. 16, 1988, describes a method of forming gel-filled cushion pads that may be heated or cooled for therapeutic purposes.
An example of a device using a gel-filled pack for cold therapy is described in U.S. Pat. No. 4,243,041, issued to Paul on Jan. 6, 1981. This patent describes a cold therapy pack used for the relief of pain, swelling, or other discomfort of patients having cosmetic surgery in the facial area. The cold therapy pack is a goggle-shaped plastic pack filled with a hydrophilic gel having the property of maintaining its pliability in a frozen state.
Therapeutic wraps containing refrigerant gels or coolants that may be wrapped around an injured limb such as an ankle, after the gels or coolants are cooled to a desired temperature, are described in U.S. Pat. Nos. 4,092,982, issued to Salem on Jun. 6, 1978, and 4,055,188, issued to Pelton on Oct. 25, 1977. A therapeutic elastic bandage containing bags filled with an antifreeze solution of propylene glycol in distilled water which may be cooled and used to cover an injured joint is shown in U.S. Pat. No. 3,900,035, issued to Welch, et al. on Aug. 19, 1975. Hot or cold compresses or wraps containing gels which may be wrapped, fit around or applied to a body part are disclosed in U.S. Pat. Nos. 3,885,403, issued to Spencer on May 27, 1975, and 3,780,537, issued to Spencer on Dec. 25, 1973, and British Patent No. 1,600,505, issued to Neave and dated Oct. 14, 1981. A hot or cold pack containing an absorbent pad, filled with a heated, cooled or frozen fluid such as water, which may be applied to a body part, is disclosed in U.S. Pat. No. 3,889,684, issued to Lebold on Jun. 17, 1975. A cold pack compression bandage containing a refrigerant gel which may be wrapped around a portion of a body is shown in European patent application No. 82302417.9 of Gordon, et al., dated Jan. 5, 1983.
Other cold pressure bandages or wraps using a refrigerant which may be fit around a body part are described in U.S. Pat. Nos. 3,717,145, issued to Berndt, et al. on Feb. 20, 1973, and 3,628,537, issued to Berndt, et al. on Dec. 21, 1971. A compression bandage impregnated with a hydrous gel for cooling and compressing an injured body part is described in U.S. Pat. No. 4,377,160, issued to Romaine on Mar. 22, 1983.
U.S. Pat. No. 4,756,311, issued to Francis, Jr. on Jul. 12, 1988, discloses a gel pack comprising an envelope fabricated from a laminate composed of film layers of dissimilar materials containing a gel composition including water, and a process of microwave heating the gel pack.
A gel pad useful in the prevention and treatment of decubitus ulcers (pressure sores) is fabricated by putting a thin-film envelope around a gel made by cross-linking high molecular weight polyvinyl alcohol, using a cross-linking agent, such as formaldehyde, in the presence of an acid catalyst such as hydrochloric acid, and by incorporating at least one internal plasticizer such as propylene glycol in the gel, is described in U.S. Pat. No. 3,858,379, issued to Graves, et al. on Jan. 7, 1975. Another gel cushion useful for protecting the body of a human or animal against localized pressures is manufactured by placing a sheet material around a gel comprising the reaction product of an organosiloxane and a hydrogenosiloxane, which is preferably a copolymer of a particular combination of siloxanes combined with an additive such as dimethylpolysiloxane, is disclosed in U.S. Pat. No. 3,663,973, issued to Spence on May 23, 1972.
Phase change materials may be used to improve the temperature storage capacity of different materials. U.S. Pat. No. 4,711,813, issued to Salyer on Dec. 8, 1987, discloses a polyethylene composition formed from cross-linked polyethylene having a straight chain (crystalline) alkyl hydrocarbon incorporated therein as a phase change material which may be manufactured as pellets or in sheet form. The polyethylene composition is for incorporation into concrete or other building materials and is used for wall or floor coverings, fire retardants, or runway, roadway or bridge de-icing, etc. U.S. Pat. No. 4,617,332, issued to Salyer, et al. on Oct. 14, 1986, describes a phase change composition comprising a cementitious matrix material selected from the group consisting of hydraulic cement, gypsum, lime and plaster of paris, and a plurality of pellets or granules containing a crystalline straight chain alkyl hydrocarbon or a mixture of crystalline, straight chain, alkyl hydrocarbons with the hydrocarbons having at least 14 carbon atoms and a heat of fusion greater than 30 cal/gm.
Encapsulated phase change materials in pellets for incorporation into concrete or other building materials are described in U.S. Pat. No. 4,504,402, issued to Chen, et al. on Mar. 12, 1985. The pellet-shaped product of this patent is formed of an outer seamless shell member which defines a cavity that permanently encases a phase change composition. The encapsulated phase change compositions described in the patent may be glauber salt eutectic mixture, sodium hydroxide, polyethylene, sodium sulfate decahydrate, sodium thiosulfate pentahydrate, calcium chloride hexahydrate, magnesium nitrate hexahydrate, the eutectic of magnesium nitrate hexahydrate and ammonium nitrate, potassium fluoride tetrahydrate, sodium acetate trihydrate, stearic acid, the eutectic of naphthalene and benzoic acid and paraffinic hydrocarbons. Shell materials described in the patent are copolymer latex of butadieneacrylonitrile, copolymer of vinylidene chloride-acrylic, resinous latexes, rubber latexes, epoxy polymers, polyurethane polymers, acrylic polymers, cellulose acetate and polyamides. Encapsulated phase change material particles are disclosed in U.S. Pat. No. 4,708,812, issued to Hatfield on Nov. 24, 1987. This patent describes encapsulated phase change material particles made by encapsulating with a continuous elastomeric, condensation polymeric shell phase change material particles selected from the group consisting of a crystalline polymer, naphthalene, salt hydrate and a crystalline paraffin.
Phase change materials that may be incorporated into building materials and used for other purposes are described in an article entitled "Advanced Phase-Change Materials for Passive Solar Storage Applications," by I. O. Salyer, et al., Society of Automotive Engineers, Inc., 1985, p. 3.699. The phase change materials discussed in this article are C-15 to C-24 crystalline alkyl hydrocarbons, tetrabutyl ammonium fluoride (and homologous) semiclathrates, acrylate and methacrylate polymers having C-16 to C-18 alkyl side chains, and polyethylene glycols having molecular weights between 600 and 3500. The phase change materials may be used for cement, concrete, plaster, plasterboard, floor tiles, foam insulation, textiles, paints, fire retardants, deicing of bridge decks and airport runways, keeping drinks at desired temperatures, etc. Another composition containing phase change material that may be used in the manufacture of building materials is described in U.S. Pat. No. 4,587,279, issued to Salyer, et al. on May 6, 1986. This patent describes a cementitious composition comprising an inorganic cementitious building material and an end-capped polyethylene glycol dispersed therein as a phase change material, the end-capped polyethylene glycol having a molecular weight greater than about 400 and a heat of fusion greater than about 30 cal/gm. The end-capped polyethylene glycol is selected from the group consisting of alkoxy-capped polyethylene glycol, urethane-capped polyethylene glycol, and ester-capped polyethylene glycol.
Polyethylene glycol has been used as a phase change material in thermal energy storage clothing. The polyethylene glycol phase change material is attached to the fibers of the clothing and absorbs large amounts of heat when it melts or softens, and releases large amounts of heat when it solidifies.